Spanish word bocadillo comes from Spanish -illo (Added to masculine nouns to denote a diminutive form.), Spanish bocado (Bit. Mouthful. Snack.)

Detailed word origin of bocadillo

Dictionary entry	Language	Definition
-illo	Spanish (spa)	Added to masculine nouns to denote a diminutive form.
bocado	Spanish (spa)	Bit. Mouthful. Snack.
bocadillo	Spanish (spa)	(Spain) sandwich. (comics) speech bubble (rounded outline, containing words, representing speech). Snack.